Method for producing hollow yarn film

a hollow yarn and film technology, applied in the direction of packaging, filament/thread forming, fastening means, etc., can solve the problems of insufficient water permeation performance, stains are deposited on the membrane, and the water permeation performance is not satisfactory, so as to achieve excellent repeated fatigue resistance, small shaking effect of fibers, and high resistance to marring

Inactive Publication Date: 2003-06-12
ASAHI KASEI KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

0093] The tensile modulus is preferably not less than 10 MPa and not more than 80 MPa, more preferably not less than 10 MPa and not more than 70 MPa, further preferably not less than 20 MPa and not more than 60 MPa. If it is less than 10 MPa, the membranes lack stiffness and they can hardly be bundled to make a module. If it is more than 80 MPa, the effect of shaking of fibers is small.
0094] Furthermore, the hollow fiber membrane obtained by the method of the present invention has the characteristics that it is high in resistance against marring and excellent in repeated fatigue resistance. In general, when membranes are marred, mars further grow from the starting points to result in leakage or breakage, while the hollow fiber membrane obtained by the method of the present invention hardly break at the mars probably because of the low tensile modulus. Especially, when the membrane has a uniform three-dimensional network structure, there is the merit that even if the surface is marred, the rejection pore diameter does not substantially change unless the mars pierce the membranes.
0095] Moreover, the membrane has ...

Problems solved by technology

The flushing method and air scrubbing method are high in cleaning effect of membranes, but they apply a great load to membranes, which is apt to cause rupture of the membranes, and, furthermore, in the case of conventional mem...

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
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  • Method for producing hollow yarn film
  • Method for producing hollow yarn film
  • Method for producing hollow yarn film

Examples

Experimental program
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Effect test

example 1

[0127] 23% by weight of hydrophobic silica having an average primary particle diameter of 0.016 .mu.m and a specific surface area of 110 m.sup.2 / g (AEROSIL-R972 (trademark) manufactured by Japan Aerosil Co., Ltd.), 30.8% by weight of dioctyl phthalate and 6.2% by weight of dibutyl phthalate (SP of mixture of these two compounds: 18.59 (MPa).sup.1 / 2) were mixed by a Henschel mixer, and to the mixture was added 40% by weight of polyvinylidene fluoride having a weight-average molecular weight of 290000 (KF polymer #1000 (trademark) manufactured by Kureha Chemical Industry Co., Ltd.), followed by further mixing by a Henschel mixer.

[0128] The resulting mixture was further melt kneaded by a 48 mm.phi. twin-screw extruder to prepare pellets. The pellets were continuously introduced into a 30 mm.phi. twin-screw extruder and melt extruded from a circular ring nozzle attached at the tip of the extruder at 240.degree. C. while supplying air into the hollow portion. The extruded product was pas...

example 2

[0131] Hollow fiber membranes were obtained in the same manner as in Example 1, except that after being drawn and leaving the second heating bath (0.8 m in length) adjusted to a space temperature of 80.degree. C., the hollow fibers were continuously passed between a pair of rugged rolls with four crests which had a peripheral length of about 0.20 m and were positioned on the water surface of a cooling water bath of 20.degree. C. at a rotational speed of 170 rpm, whereby the hollow fibers were cooled while being periodically bent, and thereafter the hollow fibers were taken off at a speed of 30 m / min by the third infinite track type belt take-off machine and were subjected to extraction and drying, followed by heat-treating the dried hollow fiber membranes at 140.degree. C. for 2 hours in an oven. The amount of silica remaining in the membranes was 0.4% by weight.

[0132] The resulting hollow fiber membranes after being subjected to the heat treatment had an outer diameter of 1.22 mm, ...

example 3

[0134] Hollow fiber membranes were obtained in the same manner as in Example 2, except that a polyvinylidene fluoride polymer having a weight-average molecular weight of 310000 (Solef 6010 (trademark) manufactured by SOLVAY Co.) was used as the polyvinylidene fluoride polymer. The amount of silica remaining in the membrane was 0.4% by weight.

[0135] The resulting hollow fiber membranes after being subjected to the heat treatment had an outer diameter of 1.22 mm, an inner diameter of 0.66 mm, a porosity of 72%, an average pore diameter of 0.27 .mu.m measured by the half-dry method, a maximum pore diameter of 0.35 .mu.m measured by the bubble point method, a ratio of the maximum pore diameter and the average pore diameter of 1.30, and a pure water permeation rate of 4700 L / (m.sup.2.multidot.hr). The membranes had a tensile break strength of 8.9 MPa, a tensile break elongation of 130%, a tensile modulus of 37 MPa, a compressive modulus of 4.4 MPa, and an instantaneous compressive streng...

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Abstract

In a method for producing hollow fiber membranes which comprises melt kneading a mixture comprising polyvinylidene fluoride and an organic liquid or a mixture comprising polyvinylidene fluoride, an organic liquid and an inorganic fine powder, extruding the kneaded mixture to form hollow fibers, and extracting the organic liquid or the organic liquid and the inorganic fine powder from the hollow fibers, which includes the steps of drawing the hollow fibers before or after termination of the extraction and then shrinking the fibers. According to this method, it is possible to stably produce hollow fiber membranes having dense pores and having a high water permeation performance, excellent endurance and stain resistance, and which are suitable for filtration uses such as removal of turbidity of water.

Description

[0001] The present invention relates to polyvinylidene fluoride hollow fiber membranes and a method for producing the same. More particularly, it relates to polyvinylidene fluoride hollow fiber membranes which have dense pores and a high water permeation performance, are excellent in endurance and stain resistance, and are suitable for uses in filtration fields such as removal of turbidity of water, and a method for producing the same.[0002] The filtration operations such as removal of bacteria and turbidity particles using porous membranes such as microfiltration membranes and ultrafiltration membranes are put to practical uses in a wide variety of fields such as the automotive industry (systems for recovery and reuse of electrodeposited paints), semiconductor industry (production of ultra-pure water), and medicine and food industries (removal of bacteria, enzyme purification). Particularly, application to the field of water supply in which potable water and industrial water are pr...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
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Application Information

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IPC IPC(8): B01D63/02B01D63/04B01D63/16B01D65/08B01D67/00B01D69/00B01D69/02B01D69/08B01D71/34C02F1/44D01D5/24D01F6/48
CPCB01D63/024Y10T428/1328B01D65/08B01D67/0027B01D67/003B01D67/0083B01D67/0086B01D67/0088B01D69/00B01D69/02B01D69/08B01D69/084B01D71/34B01D2321/04B01D2321/185C02F1/444D01D5/24D01F6/48B01D2323/46B01D2325/02B01D2325/28B01D63/16C08J9/26B01D63/04
Inventor HAMANAKA, KATSUHIKOSHIMIZU, TETSUO
Owner ASAHI KASEI KK
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